Many different products in our daily diet are derived from milk. Milk contains sugar, fats and proteins. The primary sugar in milk is lactose. Lactose is found at levels of about 2-8 percent in milk. Lactose is a disaccharide sugar composed of galactose and glucose. In the dairy industry it is often necessary to measure lactose concentrations. For example, the production of lactose-free milk requires analysis of the lactose levels in the final product and could be optimized by lactose measurements during the process.
Analytical methods that are currently used to measure the concentration of lactose in milk take samples from the milk solutions and then send them to laboratories where they are analyzed. When the milk samples are removed, and during the time it takes to test these samples, the chemistry of the sample often changes and thus the test results may be inaccurate or inconsistent. Current analytical methods have a limited range of measurement because the response of their detection element saturates, returning the same signal for two different concentrations. In order to obtain an accurate concentration measurement under saturating conditions, the solution is diluted and then measured again. This can lead to measurement errors and is not readily suitable for continuous and in-situ measurements.